1. Field of the Invention
The present invention is related primarily to the field of locking devices. More particularly, the present invention relates to the field of portable locks which may be clamped onto the side rail of a track as used in conjunction with a rail guided door or window, such as a sliding patio door or garage door.
2. Description of Related Technology
Many solutions have been proposed to the problem of securely fastening and locking a door. The primary requirement of a door locking device is that it securely fasten the door while not interfering unduly with the ability to open and close the door when desired. Usually, a locking mechanism is secured to a door as inherent part of the door or door frame structure. This approach is entirely adequate in those cases where the door is of a sufficient size and a standard configuration, such as a hinged door that is large enough to permit the entry into a room by an average person.
However, many times a door is of such an unusual configuration that an integral locking structure is not practical, either for aesthetic or mechanical reasons. In particular, sliding doors, garage doors and other track-mounted doors and windows have been difficult to lock because of the substantial planar dimensions of the door, the relative thinness of such doors, and the fact that such doors are often custom fitted to a particular application. A custom-made lock could be fabricated in each case, but such an approach would be expensive. The ideal solution to the problem of locking a track-mounted door or window would be to provide a portable locking mechanism of some sort that would be effective on a wide variety of sliding doors, regardless of their particular mounting environment.
Several types of portable locking devices have been utilized in the past. For example, in U.S. Pat. No. 1,019,226, issued to Cragie, the problem of fastening a hatch was solved by mounting a bracket to the external side wall of the enclosure, and retracting an extendable, angled arm which urged the hatch cover downwardly toward the bracket. While the hatch was free of any permanent locking mechanism, this device required that the bracket be permanently mounted to the hatch side wall.
A truly portable locking device was disclosed in U.S. Pat. No. 1,239,802, issued to MacBeth. A pair of coplanar hooks gripped the edge of a door frame, while a hook extending in the opposite direction engaged the door knob. A turnbuckle arrangement urges the oppositely-mounted hooks toward each other, thereby gripping the door knob so as to resist any force that would tend to open the door. Unfortunately, this system is not adaptable to doors which open while remaining in the plane of the door frame.
Thus, the most common solution to securely locking a track-mounted door or window has heretofore been to place a stick or rod of precise length in the door track when the door is fully closed so as to resist any movement of the sliding door member. While effective in some cases, such locking "rods" must be custom made for each particular application and therefore, while portable, may not be transferred from door-to-door unless the respective doors are of identical configuration and dimensions.